Microspheres assembled by KMn8O16 nanorods and their catalytic oxygen reduction activity in direct methanol fuel cells

• KMn8O16 microspheres are assembled by nanorods with length of 300–1000 nm.
• The KMn8O16 shows excellent tolerance toward methanol poisoning and good stability.
• The electron transfer number was measured to be about 3.98 by RRDE.
• The cost of our novel alkaline DMFC is half of conventional DMFCs.
• The performance approaches the highest value of DMFCs with noble catalysts.

Microspheres assembled using cryptomelane-type KMn8O16 nanorods are synthesized via a facile template-free, single-step hydrothermal technique. The synthesized KMn8O16 generates nanorods 10–20 nm in diameter and approximately 300–1000 nm long. The rods self-assemble to form microspheres of 2–6 μm in diameters. The electron transfer number for KMn8O16 during the ORR is approximately 3.98 at 0.5 V vs. Hg/HgO, and the H2O2 percentage is 0.66%. Moreover, a direct methanol fuel cell (DMFC) is built using KMn8O16 as cathodic catalyst, PtRu/C alloy as the anodic catalyst and a polymer fiber membrane (PFM) instead of a conventional polymer electrolyte membrane (PEM). The peak power densities (43.3 mW cm−2 and 153.9 mW cm−2) have been achieved at 25 °C and 70 °C, respectively. KMn8O16 shows good electrocatalytic activity and stability during oxygen reduction in alkaline solutions and demonstrates tolerance toward methanol poisoning.

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